Despite recent innovative progress in the therapy of heart diseases, no firm therapeutic system has been established yet for severe heart failure. A common method for treating heart failure is that of medical therapy by means of β blockers or an ACE inhibitor. Heart failure too severe to be effectively cured by such therapy is treated by replacement therapy with an auxiliary artificial heart or by heart transplantation, i.e., surgical therapy.
There are various causes for severe heart failure such that surgical therapy is needed. They include proceeded valvular disease, hyper myocardial ischemia, acute myocardial infarction and its complications, acute myocarditis, chronic cardiac failure due to ischemic cardiomyopathy (ICM), dilated cardiomyopathy (DCM) or the like, and its acute exacerbation.
Various techniques are applied to the foregoing diseases depending on their cause and severity. They include valvuloplasty, replacement, coronary artery bypass, left ventricular plasty, and mechanically assisted circulation.
It has been thought that the only way for effective treatment of cardiac failure resulting from the severely decreased function of left ventricle due to ICM or DCM is replacement therapy involving heart transplantation or an artificial heart. However, replacement therapy for severe cardiac failure patients has many problems including a constant insufficient number of donors, the necessity for continuous immunosuppression, and various other complications. Therefore, it would be difficult to say that replacement therapy is universally acceptable for treating severe cardiac failure.
In order to cope with the harsh situation surrounding heart transplantation, attempts were made for a period of time to apply other surgical therapies such as the Batista operation procedure. This procedure attracted great attention as a substitute for heart transplantation. However, its limitations recently have been identified, and efforts are being made to improve this surgical procedure and its adequate application.
Under these circumstances, regenerative medicine is being developed as a new means for treating severe heart failure.
Severe myocardial infarction or the like leads to incompetence of myocardial cells, which can further progress to the proliferation of fibroblasts and fibrosis of stroma, and eventually to heart failure. The progress of heart failure damages and kills myocardial cells. As a result, myocardial cells, hardly undergo minimum cell division, decrease in number, thereby rendering the cardiac function even more incompetent.
It is considered that an effective way to reestablish healthy cardiac function for patients that have experienced severe heart failure is by cell transplantation. In fact, the transplantation of autoskeletal myoblasts has already reached the stage of clinical application.
Recently, for this purpose, a three-dimensional sheet-shaped cell culture, for treating the heart and containing cells derived from any part of an adult other than cardiac muscle, and a method for production thereof have been realized by tissue engineering that employs temperature-responsive culture dishes (Japanese Patent Laid-Open No. 2007-528755).
Quality control is needed for putting the above-mentioned cell culture to clinical use via a quality test to establish the effectiveness and safety thereof. A quality test for a sheet-shaped cell culture involves the counting of cells constituting the cell culture and an evaluation of the cells' viability and purity. An essential procedure for such evaluation is the dissociation of the cell culture into individual cells by enzymatic digestion or the like. At present, the dissociation of a cell culture, is for example, accomplished manually by placing a batch of the cell culture in a tube, adding an enzyme such as trypsin to the tube, accelerating the enzymatic reaction in an incubator, thereby breaking the bonds between cells, stirring the tube removed from the incubator after incubation for a prescribed period of time, and observing the contents in the tube to ensure the dissociation of cultured cells. If the dissociation is not completed, the tube is put back in the incubator and then the foregoing procedure is repeated until the dissociation is completed.
The dissociation of cell cultures by enzymatic reactions should be carried out completely, with no aggregated cells remaining, so that dissociated cells can be adequately examined. On the other hand, prolonged enzymatic reactions damage cells, thereby preventing adequate cell examination. Therefore, the enzymatic reaction for cell dissociation should be carried out in as short a time as possible. This necessitates frequent observations of cells during enzymatic reactions for determining whether suitable dissociation has occurred. Nevertheless, there has been no mechanized or automated process for determining the state of cell dissociation. In fact, visual observation by an operator has been required. This procedure makes it difficult to optimize the duration of enzymatic reactions and is very labor intensive for the operator.